1. Field of the Invention
The present invention relates generally to writing implements, and more particularly to a collapsible/extensible pen.
2. Prior Art
Pens that are collapsible or retractable to some portion of their fully extended length are known in the art. Representative of such pens are U.S. Pat. Nos. 3,174,461 and 3,709,620. Mittersinker et al., in U.S. Pat. No. 6,237,627, discloses an extensible pen having a pen barrel with an expanding middle section. The pen barrel holds a retractable ballpoint pen refill cartridge When the pen is expanded, the writing tip of the refill is extended from a retracted position inside the pen barrel to a writing position, while the barrel becomes full length for comfort when writing. The pen may be collapsed for storage, which simultaneously retracts the writing tip inside the pen barrel. The disclosure includes an embodiment wherein the pen includes a cap that is adapted for attachment to a key chain. Due to the construction of the pen, the fully extended length of the pen is necessarily less than two times its collapsed length.
Katoh, in U.S. Pat. No. 4,601,599, discloses a ball-point pen capable of being easily stored in a pocket or the like when not in actual use, and of being readily adjusted to a stand-by position for writing without the possibility of unexpected projection of the pen point. The ballpoint pen is provided with a telescopic body containing a ballpoint pen refill therein, and is constructed so that the pen point is hidden when the body is collapsed and that the pen point is exposed for writing when the body is extended. The ballpoint pen is further provided with retaining means for holding the body in the collapsed condition. When not in use, the ballpoint pen can be more conveniently stored in a pocket or the like if it is made shorter than prior art ones by collapsing the body. Since the body can securely be held in the collapsed state by the retaining means, the pen point is prevented from being unexpectedly exposed. The pen point can be exposed only by extending the body. In the extended state, the overall length of the pen is as long as the length of conventional, fixed-length prior art ballpoint pens. Again, however, due to the construction of the pen wherein the construction of the barrel has only two sliding members, the fully extended length of the pen is necessarily less than two times the collapsed length of the pen.
It is desirable to provide a pen that is truly compact: that is, a pen that can be collapsed to a length that is less than half of its fully extended length, have a fully extended length that is comfortable for writing and that may be attached to a key chain or necklace or the like when not in use. Most preferably, the collapsed length of the pen should be approximately the length of a key (˜2.25 inches) so that it can be conveniently attached to a key chain, and have a fully extended length of about 5 inches—a length that is comfortable for writing.